Sharing “Allow Editing” grayed out

Question

The "Allow Editing" setting is grayed out on the Share dialog for all files within a document library.

Can someone please help me enable this?

This setting can be checked under other document libraries.

Can Share settings be restricted per document library?

Answer 1

After having Office 365 support on the phone for 1.5 hours, they concluded that this setting is disabled for a document library when you enable "require check out" under Versioning Settings.